Centrifugal atomizer and method



Sept. 10, 1963 Filed Sept. 2, 1960 c. A. KEMPF.

CENTRIFUGAL ATOMIZER AND METHOD 2 Sheets-Sheet 1 INVENTOR.

61. A YTON A. KEMPF ATTORNEYS c. A. IKEMPF CENTRIFUGAL ATOMIZER ANDMETHOD Sept. 10, 19 3 2 Sheets-Sheet 2 Filed Sept. 2, 1960 Q I A272 00fl r F Q n H y 6 w J (L /4 M M, a W f v A v/A N v 1m v 5 #w/ P/4 4 FIE 4ua/haw,

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ATTORNEYS United States Patent 3,103,311 CENTRKFUGAL ATQMIZER ANDMETl-IGD Clayton A. Kempf, Berkeley, Calilrl, assignor to ForemostDairies, Inc., San Francisco, Calif., a corporation of New York FiledSept. 2, 1960, Ser. No. 53,794 7 Claims. (Cl. 2397) This inventionrelates generally to centrifugal :atomizers and atomizing methodssuitable for use with various equipment, including spray dryers, sprayconcentrators, and the like.

Centrifugal atomizing devices for spray dryers generally employ anatomizing head mounted upon a shaft and rotated at relatively highspeed. The fluid material to be atomized is fed to the head, and as itmoves outwardly by centrifugal force it is acted upon by atomizing meanssuch as a plurality of circumferentially spaced bars. -A typicalatomizer of this type is shown in Peebles et a1. 1,939,364. In general,all such :atomizers are limited with respect to capacity, havingreference to the quantity of a given fluid feed which the atomizer willatomize to a given droplet size, by a given speed of rotation. Also itis well known that power consumption tends to be excessive for thehigher operating capacities- Attempts to increase capacity by the use ofvanes, pins, or pegs, to impart rotary velocity to the feed material,have not been effective in this respect, particularly because anyincrease in capacity gained in this manner is accompanied by excessiveand uneconomical increase in power consumption.

In general, it is an object of the present invention to provide acentrifugal atomizer which is capable of relatively high operatingcapacity without excessive uneconomical power consumption.

A further object of the invention is to provide a new centrifugalatomizer which utilizes the principles of aspiration to induce outwardmovement of the fluid feed away from the central region where the feedis introduced.

Another object of the invention is to provide a new gtomizing methodapplicable to centrifugal atomizer eads.

Additional objects and features of the invention will appear from thefollowing description in which the preferred embodiments have been setforth in detail in conjunction with the accompanying drawing.

Referring to the drawing:

FIGURE 1 is a side elevational view in section illustrating an atomizerconstructed in accordance with my invention.

FIGURE 2 is a cross sectional detail taken along the line 22 of FIGURE1.

FIGURE 3 is a view like FIGURE 1, but showing another embodiment.

FIGURE 4 is a view like FIGURE 1, but showing a further embodiment.

The atomizer illustrated in FIGURES 1 and 2 consists of a head or bodywhich may be formed of a plurality of parts assembled and mounted uponthe rotary shaft 11. The body parts are formed to provide a plurality ofpassages which extend radially as shown in FIGURE 2.

Each passage is venturi-shaped, including an inner portion 11a which isoutwardly convergent, an outer portion 11b "ice inner portion of thebody is provided with an annular space 16, in which the member '12 isaccommodated.

Means is provided for admitting controlled amounts of air into thethroat portions of all of the passages. Thus as shown in FIGURE 1, anorifice fitting 17 is mounted in the lower side of the body, and eachfitting is in communication with the associated throat 11c.

Fluid atomizing means is carried by the outer periphery of the atomizerand extends across the outer open ends of the flow passages. Thus asshown in FIGURES 1 and 2, a plurality of spaced parallel teeth or bars18 extend across the portion 11b of each passage, whereby materialdelivered through the slots or openings 19 between these bars is causedto be atomized. Such bars correspond generally to the atomizer bars usedin centrifugal atomizers of the type disclosed in said Peebles et al.patent. For handling the heavier bodied fluids, a second row of suchbars can be provided, located just inside the single row illustrated.

Various structural details can be used to form the venturi-likepassages. In the construction illustrated in FIGURES 1 and 2, the bodyis formed of the upper and lower annular plates 21 and 22, the lowerplate being attached to the hub 23. The structure 24 between theseplates can be molded or otherwise formed to provide the desiredpassages. If desired, the structure 24 can be formed of a plurality ofsegments assembled side to side, or it may be formed of :a plurality oftubes shaped to form the venturi-like passages, and surrounded by afiller medium.

It is desirable to design the passages .11 in such a manner as to obtainoptimum venturi effect. Thus the throat portion 110 of each passage canbe located at a point about one-half the distance from the axis of theshaft 11, to the periphery of the device. Also each throat may belocated a distance from the inner end of the passage portion lla whichis about two-fifths the total length of each passage.

Operation of my atomizer is as cfiollows: Assuming its use in connectionwith a spray dryer for the manufacture of a dry powdered product, suchas dried milk, it is mounted in the upper portion of 'a drying chamberwhich is adapted to receive hot air or other drying medium. The shaft 11is generally vertical whereby the body of the device is in a horizontalplane. The body may he, say, 12 inches in diameter, and may be providedwith from, say, 3 to 8 or more venturi-like passages. The throats lie ofeach passage may be annular in section and may, for example, measureabout A to 1 inch in diameter. The speed of rotation may vary withdifferent types of fluid feed, but in a typical instance may be of theorder of from 9000 to 15,000 r.p.m. Assuming that feed material is beingsupplied at a constant rate to the hollow annular member 12, in feedwell 16, such material passes through the throats 11c, and is deliveredto the bars 19, where the material forms films which break into atomizeddroplets. By virtue of the .venturi effect, a sub-atmospheric pressureexists in each throat 11c, and this has the effect of inducing flow offluid feed through the same, or, in other words, fluid feed material isvirtually sucked through the throats for delivery to the bars 18. Air iscontinually bled into each throat portion 110 through the orificefittings l7, and in effiect suchwa-ir is homog neously distributedthrough the fluid feed, thus reducing its overall density. Fee-dmaterial aerated in this manner is more readily and effectivelyatomized. In addition to the foregoing, the continual drawing in of acontrolled amount of air through the orifice fitting 17 serves toaidacceleration of fluid feed material toward the periphery of theatomizer, or, in other words, toward the bars 18.

In the embodiment shown in FIGURE 3, fluid feed material is introduceddownwardly through a hollow shaft, instead of using the annular hollowmember 12. Thus, in this instance, plates 26 and 27 are provided, whichcorrespond to the plates 21 and 22. The lower plate is secured to thehollow hub 28, which in turn is fitted upon the lowered tapered end 29of the hollow shaft 31. Fluid feed introduced downwardly through thepassage 32 in the hollow shaft passes through the openings 33, theannular space 34, and the openings 35, after which it is delivered intothe inner ends of the venturi-like passages. Plate 26 in this instanceis fitted upon the hub 28. With this construction, substantially no airis admitted to the inlet ends of the Venturi-like passages.

As shown in FIGURE 4, venturi-like passages may be provided in twotiers, and each tier may be used for the same or a separate fluid feed.Thus in this instance the hollow shaft 41 has a lower tapered endportion 42, upon which the hub 43 is mounted. The body consists ofplates 44 and 45, the lower plate being mounted upon the hub 43. Thestructures 46 and 47 are formed to provide the two tiers of venturi-likepassages 48 and 49. The structures may be separated by the intermediateplate 51, which is likewise mounted upon the hub 43. The lower tier ofpassages is supplied with fluid feed introduced through the shaftpassage 52, in the hub openings 53. The upper tier of passages issupplied with feed from the annular hollow member 54, which correspondsto the hollow member 12 of FIGURE 1. Each tier passage is provided withorifice fittings 56 and 57, corresponding to the orifice fittings 17 ofFIGURE 1. The upper fittings 56 may all communicate with a common duct(not shown), which is in communication with the atmosphere.

It will be evident that with a multi-tier atomizer as shown in FIGURE 4,a plurality of separate fluids can be atomized into a common treatmentchamber, for certain specialized treatment efiects. Also the device inthis instance has a greater capacity, whether used with a single fluidmaterial or with separate feed materials.

I claim:

1. In a centrifugal atomizer for atomizing fluid feed materials, anannular body adapted to be rotated about a central axis, means on thebody rotating therewith defining a plurality of separate venturipassages each extending in a generally radial direction, each passagehaving inner and outer portions and a restricted throat portiontherebetween, and means for introducing a fluid feedinto the inner endportions of said passages at regions located inwardly of said throats.

2. In a centrifugal atomizer for atomizing fluid feed materials, anannular body adapted to be rotated about a central axis, means on thebody for rotation therewith defining a plurality of separate Venturipassages extending in a generally radial direction, each passage havinginner and outer portions and a restricted throat portion therepassages.

3. In a centrifugal atomizer for atomizing fluid feed materials, anannularbody adapted to be rotated about a centrallaxis, rim means formedon the periphery of the body and having circumferentially spacedopenings therein, means on the body for rotation therewith extendinginwardly from said rim means and a plurality of separate definingventuri passages, each of said passages including an inner portionconvergent outwardly, an outer portion divergent outwardly, and anintermediate throat portion or" restricted cross-sectional area betweensaid inner and outer portions, said outer passage portions serving todeliver fluid feed material against the said rim portion, and means forintroducing fluid feed material into the inner end portions of saidpassages at regions located inwardly of said throat portions.

4. A centrifugal atomizer as in claim 3 together with orifice means forbleeding exterior air directly into the throat portions of saidpassages.

5. A centrifugal atomizer as in claim 1 in which two tiers of saidpassages are provided, together with separate means for introducingfluid feed material into the inner ends of said passages.

6. The method of atomizing a body of fluid, comprising the steps of:rotating said fluid about a fixed axis to cause said stream of saidfluid to flow, by centrifugal force, in a stream generally radial tosaid "axis; progressively restricting the cross sectional area of saidstream as it flows outwardly from said aXis to a predetermined value ata predetermined position, to increase the velocity thereof; introducingair into said stream at said predetermined position, to increase thevolume thereof; then progressively increasing the cross sectional areaof said stream outwardly from said predetermined position; and finallyremoving all confining restriction from said stream.

7. The method of claim 6 including the further step of breaking saidstream up into a multiplicity of smaller streams just prior to removingall confining restriction therefrom.

References Cited in the file of this patent UNITED STATES PATENTS2,357,050 McCrum Aug. 29, 1944 2,645,525 Nyrop July 14, 1953 FOREIGNPATENTS 76,954 Denmark Ian. 11, 1954 13 8,203 Sweden Nov. 25, 1944

6. THE METHOD OF ATOMIZING A BODY OF FLUID, COMPRISING THE STEPS OF: ROTATING SAID FLUID ABOUT A FIXED AXIS TO CAUSE SAID STREAM OF SAID FLUID TO FLOW, BY CENTRIFUGAL FORCE, IN A STREAM GENERALLY RADIAL TO SAID AXIS; PROGRESSIVELY RESTRICTING THE CROSS SECTIONAL AREA OF SAID STREAM AS IT FLOWS OUTWARDLY FROM SAID AXIS TO A PREDETERMINED VALUE AT A PREDETERMINED POSITION, TO INCREASE THE VELOCITY THEREOF; INTRODUCING AIR INTO SAID STREAM AT SAID PREDETERMINED POSITION, TO INCREASE THE VOLUME THEREOF; THEN PROGRESSIVELY INCREASING THE CROSS SECTIONAL AREA OF SAID 